Conventionally, a technique for a storage apparatus to autonomously manage data stored therein is known (see, for example, Japanese Laid-Open Patent Publication No. 2003-223286). Specifically, the conventional apparatus requests other storage apparatus to copy a copy unit divided from its own storage area, based on the storage status of the other storage apparatus.
A technique for restoring mirrored disks storing the same data is also known (see, for example, Japanese Laid-Open Patent Publication No. H10-133926). Specifically, every time a write operation to a first mirrored disk occurs while access to a second disk is suspended, the conventional system stores block information indicating that data have been written into the first disk. During restoration of the second disk, the conventional system copies the data stored in the first disk and indicated by the block information to the second disk.
However, the conventional techniques described above have a problem that when the enclosure to be accessed by an application running on a server is switched from the current enclosure to a newly-added enclosure, the application has to be temporarily suspended for data transfer between the enclosures.
For example, the access path has to be switched so that an operation executed by the application on the server using the logical unit number (LUN) on the current enclosure is executed using the LUN on the new enclosure. In other words, it is necessary to change the logical volume mounted by the application from the LUN on the current enclosure to that on the new enclosure, and make the logical file configuration of the new enclosure match with that of the current enclosure. In this case, the operation is inevitably interrupted since the LUN on the current enclosure cannot be unmounted during access.